Click the Exhibit button. A router is attempting to form an OSPF neighborship with another router. However, the OSPF neighborship fails to establish completely. Referring to the exhibit, what is the problem?
There is another question with different log but also interface mismatch. That is sus.
https://networksarena.wordpress.com/2017/01/01/trouble-shooting-ospf-adjacency-problems-2/
if an OSPF adjacency has one side set to the default broadcast mode, and the other side set to point-to-point mode or point-to-multipoint mode, the adjacency will fail.
ali@Router1> show log OSPFLOG
Jan 1 20:50:23 Router1 clear-log[1166]: logfile cleared
Jan 1 20:50:24.565357 OSPF rcvd Hello 10.100.12.2 -> 224.0.0.5 (ge-0/0/1.112 IFL 71 area 0.0.0.0)
Jan 1 20:50:24.565388 Version 2, length 48, ID 163.121.1.2, area 0.0.0.0
Jan 1 20:50:24.565394 checksum 0x0, authtype 1
Jan 1 20:50:24.565400 mask 255.255.255.252, hello_ivl 10, opts 0x12, prio 128
Jan 1 20:50:24.565406 dead_ivl 40, DR 10.100.12.2, BDR 0.0.0.0
Jan 1 20:50:24.565412 OSPF packet ignored: configuration mismatch from 10.100.12.2 on intf ge-0/0/1.112 area 0.0.0.0
ed@vMX_R2# show protocols ospf area 0.0.0.1 | display set
set protocols ospf area 0.0.0.1 nssa default-lsa default-metric 50
set protocols ospf area 0.0.0.1 nssa no-summaries
set protocols ospf area 0.0.0.1 interface em1.2
[edit]
ed@vMX_R2# run show log ospf-log.txt
...omitted ...
Nov 14 14:45:13.913959 OSPF packet ignored: configuration mismatch from 10.0.24.4 on intf em1.2 area 0.0.0.1
Nov 14 14:45:23.402365 OSPF packet ignored: configuration mismatch from 10.0.24.4 on intf em1.2 area 0.0.0.1
Nov 14 14:45:33.121895 RPD_OSPF_NBRUP: OSPF neighbor 10.0.24.4 (realm ospf-v2 em1.2 area 0.0.0.1) state changed from Init to 2Way due to 2Way)
Nov 14 14:45:33.215716 Formatting error in LSA
Nov 14 14:45:33.216048 RPD_OSPF_NBRUP: OSPF neighbor 10.0.24.4 (realm ospf-v2 em1.2 area 0.0.0.1) state changed from Loading to Full due to L)
Nov 14 14:45:33.648589 Formatting error in LSA
But JunOS can detect MTU mismatch and generate an explicite log "MTU mismatch". Same for area mismatch. We can see in logs that OSPF hello are send with ip address which match the mask, so the configuration mismatch come from the interface type.
https://netdevops.me/2015/06/ospf-neighbors-on-a-point-to-broadcast-network/
upvoted 4 times
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